The present invention relates, in general, to the field of operating an active suspension of a motor vehicle.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
An active suspension, with which, e.g., operation in all four quadrants is controlled, is used to significantly reduce a movement of the vehicle body when travelling along an uneven roadway. Active control elements of the active suspension are hereby activated in such a way that the control elements maintain the body still by equalizing a body movement. The difference to a passive or semi-active suspension resides in a temporary addition of power to the control elements of the active suspension to stabilize the body and not only in a dissipation of power, so that the body can be stabilized more effectively.
As the motor vehicle travels, various faults may be encountered, which are caused, for example, as a result of incorrectly installed sensors, calculation errors by a control unit, transmission faults in a network (bus), etc., so that actuators of the motor vehicle are incorrectly operated. In the event of an encountered fault, there is a chance that control variables have no damping effect on a body movement, but instead the body is subject to excitation from a road profile. In other words, the energy of a vibration of the body is increasingly stimulated or stoked further, ultimately causing a so-called resonance disaster, with the movement of the body becoming unstable. This is possible only when an active suspension is involved because in contrast to passive or semi-active suspensions, power can be added into the system only in an active suspension. Conventional techniques for avoiding faults are not focused on the behavior of the motor vehicle in a closed-loop control circuit but are experienced only at a lower level, e.g. when calculating checksums for a signal transfer or a mutual plausibility of several signals.
As a profile of a terrain, normally a road, excites the motor vehicle during travel but is unknown, and only a reaction of the motor vehicle can be measured as it travels on the road, it is difficult to check the presence or absence of excitation. There is no way to distinguish whether a measuring variable, such as, e.g., the acceleration, progressively increases because the motor vehicle is subject to excitation from the road, which means that a damping function would be in order, or because the actuators of the suspension causes increasingly greater control variables as a result of a faulty control, which means that the damping function would not be in order. If there is no possibility to identify excitation, the function cannot be disabled in the event of a fault so that a power circuit has to be cut to reduce occurring vibrations again.
It would therefore be desirable and advantageous to address prior art shortcomings.